What were the two given names represented by the initials C.S. in C.S. Lewis?

The initials in C.S. Lewis stand for Clive Staples.

Lewis was born Clive Staples Lewis, and he commonly published under the initials C.S. Lewis. The name “Clive” was used in childhood, although he later adopted the nickname “Jack,” which became the name used by friends and colleagues. “Staples” was a family name inherited through his mother’s family.

The initials helped give his published work a distinctive identity across several genres. Lewis wrote literary criticism, Christian apologetics, fiction, sermons, and works for children. His byline appears on books such as The Problem of Pain, Mere Christianity, The Screwtape Letters, and The Chronicles of Narnia.

A frequent mix-up is assuming that the initials represent a longer version of “Lewis” or a title. They are simply the first letters of his two given names. “Jack” was his personal nickname, not part of the initials used on his books.